The present disclosure relates generally to inspecting a component for hole blockages and, more specifically, to inspecting a component using pressure-sensitive material to determine its film cooling efficiency.
In a gas turbine engine, air pressurized in a compressor is mixed with fuel in a combustor to generate hot combustion gases. Energy is initially extracted from the gases in a high pressure turbine (HPT) that powers the compressor, and subsequently in a low pressure turbine (LPT) that powers a fan in a turbofan aircraft engine application, or powers an external shaft for marine and/or industrial applications. Generally, engine efficiency increases as the temperature of combustion gases is increased. However, the increased gas temperature increases the operating temperature of various components along the gas flowpath, which in turn increases the need for cooling such components to facilitate extending their useful life.
For example, at least some known gas turbine components, such as blades, nozzles, and liners, require cooling during operation of the gas turbine engine. In at least some gas turbine engines, flowpath components exposed to hot combustion gases are cooled using compressor bleed air. For example, at least some known components channel the compressor bleed air through film cooling holes defined within the gas turbine components. Film cooling holes are typically formed by machining elongated passageways within the component, which is a time-consuming and complicated task, such that the holes are sometimes improperly formed, thereby reducing their film cooling efficiency. Film cooling holes may also occasionally become blocked during operation of the gas turbine engine, such as by particles entrained in the compressor bleed air. One known method of inspecting a component for film cooling blockages is to coat the component with pressure-sensitive paint, which is sensitive to local variations in the pressure of oxygen such that a flow distribution of cooling fluid discharged from the film cooling holes may be determined. However, coating a component with pressure-sensitive paint, which includes applying the paint to the component and curing the component at elevated temperatures, can be a time-consuming and laborious task.